System for producing spring coils with two reduced diameter end sections

ABSTRACT

A coil spring forming system allows for forming reduced diameter ends at both ends of a coil spring in a single forming process. A rotating member supports one end of the coil spring and preferably includes a die portion that establishes a configuration of that end of the coil spring. A pitch controlling device guides the coil stock longitudinally along the axis of the spring as the rotating member rotates to establish the desired pitch of the coil spring. A moving mandrel member is guided along an axis of the coil spring so that the mandrel member and the pitch controlling member establish the desired diameter of the spring at the corresponding portion of the spring. The mandrel member preferably has a forming surface with a varying outside dimension so that, depending on the placement of the mandrel relative to the coil stock and the pitch controlling member, the diameter of the resulting coil spring can be varied along the length of the spring. A controller preferably coordinates movements of the rotating member, the pitch controlling member and the mandrel member to establish the desired coil spring configuration in a single forming process.

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to making spring coils. More particularly, this invention relates to a system for making spring coils having reduced diameter end sections.

[0002] In many instances, it is desirable to have reduced diameter ends on a wound coil spring. One example application for such springs is in automotive suspension systems.

[0003] The traditional method of producing hot wound coil springs includes using a quill-type retractable mandrel. According to the traditional method, the quill mandrel must be withdrawn from the inside of the hot-formed spring after the stock material has been coiled. This retraction of the mandrel precludes forming a reduced end at each end of the spring in a single manufacturing step. Traditional mandrels do permit forming one reduced end but forming a reduced diameter second end of the spring requires a secondary operation. This introduces inefficiencies, which render the manufacturing process more expensive and in some cases less reliable.

[0004] Requiring a secondary operation increases the overall production cycle time, which corresponds to lower manufacturing efficiency. Additionally, the time that the spring remains outside of a quench bath after the initial forming step can have detrimental metallurgical results. Similarly, the additional handling of the hot spring during the secondary forming operation increases the possibility that the spring surface can be marked, which can lead to a stress concentration and potential early fatigue of the spring in service. Another disadvantage to conventional methodology is that the number of reduced turns on the second formed end is limited because of the fixturing and tooling issues involved in the secondary operation.

[0005] There is a need for an improved technique for making coil springs having reduced diameter ends at opposite ends of the spring. This invention addresses that need while avoiding the shortcomings and drawbacks of the prior art.

SUMMARY OF THE INVENTION

[0006] In general terms, this invention is a system for forming spring coils having reduced diameter ends at both ends of the coil.

[0007] A system designed according to this invention includes a rotating member that is adapted to support one end of coil stock. A pitch controlling member is adapted to contact the coil stock such that the pitch controlling member establishes a pitch of the coil spring along an axis of the spring. A mandrel member has an outside dimension that varies along a length of the mandrel member. The mandrel member is moveable parallel to the axis of the spring. The pitch control member cooperates with the mandrel member to establish a configuration of the coil spring as the coil stock is rotated by movement of the rotating member.

[0008] A controller preferably coordinates and controls the movement of the mandrel member and the pitch control member so that the resulting coil spring configuration is as desired. The controller preferably also controls the rotation rate of the rotating member so that the coordinated movements of the rotating member, mandrel and pitch controlling member all provide the desired coil configuration.

[0009] The coil stock preferably is heated before being supported on the rotating member and then cooled immediately after the spring is formed during a single spring forming process.

[0010] The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 schematically illustrates a system for forming a coil spring having two reduced ends, designed according to this invention.

[0012]FIG. 2 schematically illustrates selected portions of the example embodiment of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As seen in FIG. 1, a system 20 facilitates utilizing coil stock 22 to form coil springs 24 having reduced diameter end sections at both longitudinal ends of the coil. The coil stock 22 preferably is first heated in a conventional manner in a heating station 26. A material handler 28 facilitates moving the heated coil stock from the heating station 26.

[0014] The material handler 28 preferably positions the coil stock so that one end of the stock is supported by a rotating member 30, which may be referred to as a chucking device. A die portion 32 on the rotating member 30 preferably establishes a configuration of one end of the coil spring 24. The illustrated example (as can be best appreciated from FIG. 2) includes a holding portion 33 that cooperates with the die portion 32 to maintain the end of the coil spring stock in a position so that the stock is rotated as the rotating member 30 rotates. The illustrated example includes a motorized mechanism 34 that provides the necessary amount of rotation to the rotating member 30. The inventive arrangement preferably includes a motorized mechanism 34 that is strong enough to allow the rotating chucking device 30 to provide the initial shape and the necessary rotational forces to draw the heated coil stock 22 into the coiling apparatus.

[0015] As the coil stock is rotated, a pitch controlling member 40 preferably guides the stock longitudinally along the axis of the coil spring to establish the pitch of the spring. The illustrated example includes a motorized mechanism 42 for moving the pitch controlling member 40 in at least two directions for adjusting the pitch and guiding the coil stock along the spring axis during the forming process. A roller 44 preferably contacts the coil spring stock directly and guides it longitudinally as the rotating member 30 rotates. The pitch controlling member in the illustrated example is capable of moving at least in a first direction parallel to an axis of the coil and in a second direction perpendicular to the axis of the coil.

[0016] A mandrel member 50 includes a forming surface 52 that has a varying outside dimension. A motorized mechanism 54 facilitates moving the mandrel member 50 along the axis of the coil spring during the forming process.

[0017] In the illustrated example, the forming surface 52 is generally conical in shape having a reduced end 56 and a larger diameter end 58. A sloping profile of the shaping surface 52 extends between the two ends giving the mandrel the generally conical shape.

[0018] A controller 60 preferably controls the timing and coordinated movements of the rotating member 30, the pitch controlling member 40 and the mandrel member 50. By coordinating the movements of those devices, the desired configuration of the coil spring 24 can be established during a single forming operation. The mandrel member 50 preferably is moved along the axis of the spring so that the appropriately dimensioned portion of the forming surface 52 is in contact with the coil spring stock as it is guided by the pitch controlling member 40. By positioning the reduced end 56 into a coil stock contacting position, a reduced diameter to the corresponding portion of the coil spring is formed. Positioning a larger portion of the mandrel forming surface 52 into position to be contacted by the coil stock and guided by the pitch controlling member 40 establishes a larger diameter to the corresponding portion of the coil spring 24′.

[0019] The mandrel member 50 preferably is moved longitudinally along the axis of the coil spring so that the appropriate portion of the forming surface 52 is in position to establish the desired dimensions of the coil spring at the corresponding portion along the axis of the spring. The mandrel configuration and the movement of it during the forming process allows for a reduced diameter end to be established at both ends of the coil spring during a single forming operation.

[0020] The illustrated example includes a separate follower member 64 that is controlled to move into position to guide the terminal end of the coil stock against the forming surface 52 of the mandrel member 50 so that the end of the spring 24′ is established as needed. In examples where the end of the spring needs to be formed in a fashion that cannot be accommodated by the mandrel forming surface 52, the follower member 64 is operative to establish the desired configuration.

[0021] Immediately after the coil spring 24′ is formed in the desired configuration, it is transferred to a cooling station 70, which includes a conventional quench bath in one example. After appropriate cooling, the coil spring 24 can be treated as needed or prepared for shipment as desired.

[0022] Once the coil spring 24′ is formed as desired, the handling mechanism 28 preferably transfers the formed coil into the cooling station 70.

[0023] The material handler 28 includes a suitable gripper portion for handling the heated, wound material. The illustrated example includes a single handling mechanism 28 that is capable of transferring the coiled stock from the heating station 26 to the rotating member 30 and then later to transfer the heated, wound coil 24′ to the cooling station 70. Other examples include multiple handling mechanisms each designed to perform a dedicated function.

[0024] The controller 60 preferably is programmed to time the various movements of the portions of the system 20 to establish the desired coil spring configuration. Given this description, those skilled in the art will be able to suitably program a microprocessor or computer to realize a desired coil spring configuration, given the characteristics of the particular manufacturing machinery and the material used to form the spring.

[0025] The inventive arrangement provides a significantly improved manufacturing process where a single forming operation includes the ability to form reduced diameter ends at both ends of a coil spring. Because farther handling requirements are significantly reduced, the integrity of the resulting spring is also enhanced.

[0026] The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims. 

We claim:
 1. A device for making a coil spring, comprising: a rotating member that is adapted to support one end of coil stock; a pitch controlling member that is adapted to contact the coil stock such that the pitch controlling member establishes a pitch of the coil spring along an axis of the spring; and a mandrel member having an outside dimension that varies along a length of the mandrel member and that is moveable parallel to the axis of the spring, the pitch controlling member cooperating with the mandrel member to establish a configuration of the coil spring.
 2. The device of claim 1, including a controller that controls movement of the mandrel member and the pitch controlling member such that the coil spring configuration is as desired.
 3. The device of claim 2, wherein the controller controls movement of the rotating member.
 4. The device of claim 1, including a finishing member that is adapted to keep an end of the coil stock opposite from the one end supported by the rotating member in conformance with a corresponding portion of the mandrel member to establish the configuration of the corresponding end of the coil, the finishing member being selectively moveable relative to the mandrel member.
 5. The device of claim 1, wherein the rotating member includes a die portion that has a shape that establishes the configuration of the coil spring at the end that is supported by the rotating member.
 6. The device of claim 1, wherein the mandrel member is at least partially conical having a first end and a second, larger end and wherein the first end is oriented toward the rotating member.
 7. The device of claim 1, wherein the pitch controlling member is moveable in at least two directions relative to the axis of the coil spring.
 8. The device of claim 7, wherein the pitch controlling member is independently moveable parallel to the coil spring axis and perpendicular to the coil spring axis.
 9. A method of forming a coil spring, comprising the steps of: (A) rotating a piece of coil stock; (B) guiding the coil stock axially along an axis of the coil such that a desired pitch is established along a length of the coil; and (C) varying an outside dimension of the coil turns by moving a mandrel member that has a varying outside dimension axially relative to the coil stock and causing the coil stock to conform to a corresponding portion of the mandrel member.
 10. The method of claim 9, including providing a rotating member that supports one end of the coil stock, a pitch controlling member that guides the stock to establish the desired pitch and coordinating movements of the rotating member, the pitch controlling member and the mandrel member to achieve the desired coil configuration.
 11. The method of claim 9, including supporting one end of the coil stock on a rotating member and forming a first end of the coil using a die portion of the rotating member.
 12. The method of claim 9, including establishing a first reduced diameter near ends of the coil spring and establishing a second, larger diameter near a central portion of the coil spring.
 13. The method of claim 12, including forming the entire coil in one forming operation.
 14. The method of claim 12 including heating the coil stock before performing steps (A) through (C) and cooling the coil spring immediately after performing step (C). 